Oil spraying into airbox from crankcase breather
 

An unusually large quantity of oil is spraying into the airbox of my '99 tt600r.
Seems to be pretty constant.
Power is good and compression good. Starts great etc.
New piston, rings and valve stem seals about 5000 miles ago. I ran the bike in gently for 1000+ miles.
Unfortunately until a couple of thousand miles ago i had a leak from the oil filter cover. This was repaired with helicoils in the bolt holes, but since then ive had this oil problem.
Any ideas?

Where to start looking ...
 

Usually, such a thing is caused by excessive pressure built-up in the crankcase. This is caused by combustion gases somehow entering the crankcase. And this can happen via two ways: past the piston and past valve stem seals.
Just assuming your piston is OK, did you install genuine Yamaha valve stem seals or the sh*tty aftermarket stuff? Are they still correctly located?

Also, rethreading the lower bolt hole of the oil filter cover is tricky: the oil to the crankshaft passes along the bolt. If you thread in the wde paryt of the hole and screw a bolt in there the passage is wholly or partly blocked.....
So, this is also a thing to make sure.

And, last but should be first: is your oil level not too high. Checking is close to sorcery and therefore liable to go wrong with overfilling as result. (Run engine under load for at least 15 mins, let idle for 1 minute, switch of and immediately check level, this is the only way to do it correctly).

Auke

You should do the same everytime you need to recheck (after topping up)!

For some reason you have to start the engine and have the oil pumped around a bit before you will see any impact of topping up on the dip stick!

Jens

Thanks for the ideas guys
 

I'm pretty sure the piston and rings are good. I had the bike dynoed and it made plenty of power, so i reckon compression should be good.
Valve stem seals are genuine Yamaha, as are all other parts and were installe d correctly.
I haven't checked the lower bolt hole since it was repaired(not by myself, so i don't know where mechanic added thread). When we fired the bike up and bled the oil filter chamber the flow of oil out of the bolt was weaker than usual. A sign?
The oil level is correct. Im fully aware of the ridiculous procedure! I agree with the sorcery comment......

Many thanks for the replies, i've got a feeling its something to do with the threads in the oil filter cover.

chris

I've only got my expirences with early xt motors(83-85) to go on but I belive your tt is basicly the same, If not hopefull I'll be corrected.
I have repaired the threads for the filter cover and looked closely at the passageway in the lower bolt hole, it is not a feed to the crankshaft. Its only purpose is to drain the oil from the filter housing back into the engine once the bolt is removed, to prevent a huge mess when changing the filter. I have blocked this with a helicoil some 15000 km ago, and yes, it dose make a mess.


You said the motor was dynoed and made lots of power, how much?
One of the problems of making more horsepower with this motor is getting the crankcase to breath, the base is vented on the clutch side and across the hollow balencer shaft into a cavity and up to the breather, there is a only a lip seal on end bearing. its possible this has blown out and oil from the crankshaft is being pushed out the vent.

Caution!
 

Sorry to disagree Winmac, but there is indeed an oil channel leading off the hole for the bolt. I might be mistaken in that it does not go to the crankshaft, but somewhere else, but blocking it is not a good idea.

Auke

hi guys i just got an xt600e 2002 friday past and noticed the same the same thing in the air box when i was having a look over the bike.im glad i found this forum already as i would never of new about the procedure for checking the oil (no manual) 1 thing i was wondering is the oil level on the diper to be took from when it is screwed into the thread or dipped from the top of the thread sounds stupid i no but new to 4 strokes and this hole oil inthe frame thing

thanks in advance

and i hope ya dont mind me jumping onto ur thread m8
:thumbup1: :thumbup1: :thumbup1:

This thread may be the answer to my questions about excessive oil pressure (hence I nuked my new subject). I am going to bet that my XT oil tank bulged because I had too much oil of 10w40 grade. I am now running 2.5L of 20w40 measured to half the stick using aukeboss' method. I will post if my problems go away or not.

Top of the thread.

thanks :thumbup1:

i had the same probs with my 89 xt tenere on my ride to mongolia. if you look at the air box there is a drainage hole on it for the oil to seep out on the left which is probably how you noticed it. so it is probably supposed to leek abit, not sure why but maybe its to keep the air filter oiled to catch the dust. i have always had that problem but never caused any problem with the bike. oil got low every now and then but not by much. mine did leak quite bad when i first bought the bike but that was due to me over filling it, the best way to top the oil up is a mentioned as before, top up a bit, let her run for a bit then top her up some more. i never bothered with the dipstick as the tank is only a top up tank, as long as your tank is half full you good to go, any higher ie 3/4 full, you start getting alot of oil in your air intakes and she starts to smoke.
from what i found all xt's leak abit, i rebuilt mine from scratch for my ride, john, one of the other lads on the trip had his built for him and both of them leaked in the same places a little, its just the way it is, usualy from the alternator cover by the bottom dowl, the air box and from the the bottom of the crank case breather, as long as you not dramaticaly loosing oil in your oil tank, dont worry about it, they usualy block themselves up. xt are very hard to kill. great choice in bike and fantastic fuel concumption.
also. dont put semi oil in an xt cause it makes you clutch slip, only use mineral oil.
look at the punishment mine took. up dating the site soon

www.horizonsunlimited.com/tstories/patrick